Catching Exception of a function in a procedure

Question

Hi,
I have a procedure named P calling a function named F. If function F returns no value.. I want to catch that exception in the procedure/function itself and display to the user that the function named F has returned without any values.
Thanks in advance

Answer 1

A function not returning a value, is an error in the function. A bug in the function's code.
A function must return a value, or raise an exception. It cannot simply just not return a value.
E.g.create or replace function F ( n number ) return BOOLEAN is
b booloean := FALSE;
begin
.. do some stuff ..
if <some condition> then
-- an error has occured - raise an exception
raise_application_error( -20001, 'blah blah' );
end if;
return( b );
end;This code is however ugly. The RAISE_APPLICATION_ERROR is a system call. If you want to trap all calls in your code that raises an exception, you have a problem. Also, the exception number is hardcoded.
It is better to have a procedure called RaiseException and have it make the call to RAISE_APPLICATION_ERROR. This way you have a single place in all your code where this system call is made. You can easily add logging and debugging into that single place. Dump the PL/SQL stack. Etc.
And of course, replace the hardcoded number with a constant.
In the procedure, you will trap the exception using an exception handler. E.g. create or replace procedure P is
  b boolean;
  n number;
begin
  .. do some stuff ..
  b := F( n );
  .. do some more stuff ..
exception
  when <some_exception> then
    .. code to handle the exception..
end;
Refer to the Oracle® Database PL/SQL User's Guide and Reference for details on how to create custom exceptions, raise exceptions, and trap exceptions.